Lte magazine: currently, we transmit one hundred terabits per second over a single strand of optical fiber. Will we one day reach a theoretical limit of optical fiber that we can not exceed?
Mr. Peter Schultz: Yes. There is a fundamental limit of information capacity which is imposed by the frequency or wavelength of the light which carries the optical signal over a fiber. Even at the theoretical minimum in attenuation of signal strength, and even if all other signal impairments are eliminated, the maximum capacity will be dictated by this “carrier” frequency. Details will depend on parameters such as distance travelled and signal coding, but the only solution once this capacity limit is reached is to increase the number of optical signal paths. The simplest way to do this is with more fiber.
Lte magazine: in 1986, I personally visited the Siemens laboratories in Munich (Germany) where I saw an optical telephone switch operated with light. Do you think that one day we will arrive at optical services from end to end and 100% optical without going through the optoelectronic transformation.
Mr. Peter Schultz: In principle, light can be controlled with light, but this typically is not a very efficient process and requires either relatively high optical power, or long path lengths. Also, a critical limitation of optical devices or circuits is that light cannot be stored very efficiently, posing an impediment to functions such as buffering. As transmission capacity increases, power efficiency and size become very critical so the best solutions are those which take advantage of the best properties of both light and electronics.
Lte magazine: Since the end of the 1990s, plastic fibers based on polymers have started to appear on the market, alongside optical fiber based on silicon. What is the future of both technologies and their future applications? Mr. Peter Schultz:: There are several key differences between plastic and silica-based optical fiber which determine their applications. Communications technology has evolved to operate at a wavelength in the mid-infrared region where silica fiber has extremely low loss. Also, to maximize capacity, the light-guiding portion of the fiber is very small and is controlled very precisely. Plastic fiber, on the other hand, has fundamentally high loss at communications wavelengths and must be relatively large. This limits the applications of plastic fiber to relatively short distances where information capacity does not have to be maximized. Applications for plastic optical fiber take advantage of specific attributes such as ease of handling and installation, such as connections to consumer electronics or in automotive applications. As data generation and processing increase, bandwidth will increase and be pushed closer to the consumer device. This will increase both the application space and volume of plastic fiber. Lte magazine: what advice or recommendation would you give to young African scientists to tame new communication technologies?
Mr. Peter Schultz: Most important, they should keep up-to-date with the latest developments in their field through technical publications, attending world-class conferences such as OFC and ECOC, and taking pertinent continuing education courses. Next, they should seek a mentor with whom they can discuss these latest developments and find out what the current technical challenges are that need solutions. This mentor can be for example an industry or university colleague or advisor. Finally, when working on cutting edge problems, try to look “out-of-the-box” for solutions, rather than pursue the same path that others are taking. The best solutions are often the “simplest” and “obvious”, but only in hindsight!